1. Field of the Invention
The present invention relates to gas storage and dispensing systems in general, and more specifically to hydrogen storage systems and fuel cell systems with hydrogen storage capacity.
2. Description of the Related Art
Safe, capacious, and convenient storage for various industrial gases is an important aspect common for many industrial operations. When such gases are explosive, toxic, or otherwise environmentally hazardous, the costs for storing and transporting such gases will significantly increase, causing the overall operational costs to rise correspondingly. Even with increased costs, the safety of such storage and transportation is still not guaranteed, and gas leakage/burst due to equipment malfunction or system failure is not infrequent, imposing great danger to the life and health of those persons living or working in the vicinity of such gas leakage/burst sites.
The most common gas storage method is high-pressure (2000-3500 psi) storage in steel gas cylinders. There are many types of high-pressure gas storage cylinders, which contain toxic and other hazardous gases or liquefied gases. These high-pressure gas storage cylinders fill and empty quickly without complications. However, use of such high-pressure gas storage cylinders is significantly limited, due to the danger of explosively rapid release of gas in case of leaking. Moreover, the high-pressure gas storage cylinders have to be built with thick, heavy steel cylinder walls for enduring the high interior gas pressure as well as for ensuring safety against impact, puncture, or crushing damage. The heavyweight cylinder walls significantly limit the overall mass fraction storage capacity of such high-pressure gas cylinders.
Another commonly used gas storage method is liquefied gas storage at very low temperatures. Cryogenic storage, however, consumes a large amount of energy, and the liquefied gas is also not safe or practical for most consumer applications.
Other methods for gas storage include the use of physical or chemical sorbent materials for reversibly adsorbing and releasing the stored gas, which does not require application of high pressure or low temperature. However, the gas storage capacity of such physical or chemical sorbent materials is usually very limited, and the actual working capacity of such sorbent material (i.e., the actual amount of stored gas that is recoverable through desorption) is further limited by large amount of gas sorbate that is trapped in the sorbent bed and becomes irrecoverable. Moreover, the adsorption and desorption speed of the stored gas is significantly limited by diffusion rate of such gas through the sorbent materials, and complicated thermal or pressure equipment is required for enhancing the adsorption/desorption speed.
It is therefore an object of the present invention to provide a gas storage system with enhanced gas storage capacity, reduced storage/transportation cost, and reduced risk of leakage/rupture in comparison with the conventional gas storage methods as described hereinabove.
Hydrogen gas is recognized as an environmentally desirable clean fuel of the future, since the conversion of chemical energy in hydrogen into electrical energy by fuel cells only generates heat and water as end products in a clean and quiet manner with little or no undesirable environmental impact.
Using hydrogen gas as a fuel, however, presents a challenge for the development of hydrogen-fueled vehicles and hydrogen-based energy generation systems. Although hydrogen is extremely energy rich on a weight basis, it is relatively energy poor on a volumetric basis, in comparison with gasoline, and large volumes of hydrogen gas must be safely stored and transported for providing fuel to vehicles and for generating electrical energy for industrial usage. Currently, efficient, low cost, safe, onboard hydrogen storage and transportation systems are still not available.
It is therefore another object of the present invention to provide an efficient and safe hydrogen storage system with enhanced gas storage capacity and reduced cost.
Further, U.S. Pat. Nos. 5,916,514; 5,928,808; 5,989,300; 6,004,691; 6,338,913; 6,399,232; 6,403,248; 6,403,517; 6,444,339; and 6,495,281, all to Ray R. Eshraghi, describe a microcell technology, which relates to microfibrous electrochemical cell structure comprising hollow fiber structures with which electrochemical cell components are associated.
The aforementioned Eshraghi patents specifically describe a microfibrous fuel cell, which has an inner current collector, a hollow fibrous membrane separator containing an electrolyte medium, an outer current collector, and an inner and outer electrocatalyst layer on the inner and outer surface of the membrane separator. One embodiment of such microfibrous fuel cell is a hydrogen-based fuel cell, wherein hydrogen gas is supplied at one side of the hollow fibrous membrane separator, and oxidant is supplied at the other side of the hollow fibrous membrane separator, so that the chemical energy stored in hydrogen gas is converted into electrical energy, generating water and heat as by-products.
Such hydrogen-based microfibrous fuel cell as described in the Eshraghi patents depends on an external hydrogen source for providing the hydrogen gas needed.
It is therefore a further object of the present invention to provide an improved hydrogen-based microfibrous fuel cell with hydrogen storage capacity, which can be used to generate electrical energy independent of any external hydrogen source. Such self-sufficient, independent, microfibrous fuel cell is ideal for supplying electrical energy to various small-size mobile devices such as cell phones, laptop computers, personal digital assistant (PDA), etc.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.